linux-kernel - Re: [RFC PATCH 1/6] security/fbfam: Add a Kconfig to enable the fbfam feature

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Message-ID: <CAG48ez1V=oVczCCSuRaWX=bbN2cOi0Y9q48=e-Fuhg7mwMOi0A@mail.gmail.com>
Date:   Thu, 10 Sep 2020 23:21:58 +0200
From:   Jann Horn <jannh@...gle.com>
To:     Kees Cook <keescook@...omium.org>, John Wood <john.wood@....com>
Cc:     Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Matthew Wilcox <willy@...radead.org>,
        Jonathan Corbet <corbet@....net>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Iurii Zaikin <yzaikin@...gle.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>, linux-doc@...r.kernel.org,
        kernel list <linux-kernel@...r.kernel.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        linux-security-module <linux-security-module@...r.kernel.org>
Subject: Re: [RFC PATCH 1/6] security/fbfam: Add a Kconfig to enable the fbfam feature

On Thu, Sep 10, 2020 at 10:21 PM Kees Cook <keescook@...omium.org> wrote:
> From: John Wood <john.wood@....com>
>
> Add a menu entry under "Security options" to enable the "Fork brute
> force attack mitigation" feature.
[...]
> +config FBFAM

Please give this a more descriptive name than FBFAM. Some name where,
if a random kernel developer sees an "#ifdef" with that name in some
random piece of kernel code, they immediately have a rough idea for
what kind of feature this is.

Perhaps something like THROTTLE_FORK_CRASHES. Or something else that
is equally descriptive.

> +       bool "Fork brute force attack mitigation"
> +       default n

"default n" is superfluous and should AFAIK be omitted.

> +       help
> +         This is a user defense that detects any fork brute force attack
> +         based on the application's crashing rate. When this measure is
> +         triggered the fork system call is blocked.

This help text claims that the mitigation will block fork(), but patch
6/6 actually kills the process hierarchy.